Debt (Principal Payments On Mortgage Payable, Notes Payable, Senior Notes and Debentures) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Debt Instrument [Line Items]
2012	$ 204,173
2013	208,551
2014	307,838
2015	204,936
2016	136,921
Thereafter	974,363
Long-term Debt	2,036,782	[1]
Mortgages Payable [Member]
Debt Instrument [Line Items]
2012	18,444
2013	73,521	[2]
2014	157,838
2015	204,936
2016	2,521
Thereafter	280,163
Long-term Debt	737,423	[1]
Notes Payable [Member]
Debt Instrument [Line Items]
2012	10,729
2013	30
2014	0
2015	0	[3]
2016	9,400
Thereafter	275,000
Long-term Debt	295,159	[1]
Senior Notes and Debentures [Member]
Debt Instrument [Line Items]
2012	175,000
2013	135,000
2014	150,000
2015	0
2016	125,000
Thereafter	419,200
Long-term Debt	$ 1,004,200	[1]

[1] The total debt maturities differ from the total reported on the consolidated balance sheet due to the unamortized discount or premium on certain senior notes, debentures and mortgages payable.

[2] Includes the repayment of the outstanding mortgage payable balance on Mount Vernon. The lender has the option to call the loan on April 15, 2013 or any time thereafter.

[3] Our $400.0 million revolving credit facility matures on July 6, 2015, subject to a one-year extension at our option. As of December 31, 2011, there was $0 drawn under this credit facility.